Most electronics rely on integrated circuit technology. A thin substrate of semi-conductor made of passive elements and electronic circuits is miniaturized to form what is known as a microchip, a microprocessor, or a chip. Leads initially in the form of pins or wires have been progressively replaced by factory applied solder balls and shaped by surface tensions of liquid solder balls. These balls are generally arranged on the chip in an array over a single surface. Chips mounted with solder balls are generally referred to as Flip Chips. Flip Chip structures are typically mounted on a substrate which contains interconnect circuitry to facilitate connecting the solder balls (or bumps) on the chip to larger more widely spaced solder balls on the other side of the substrate. This allows for the resulting Flip Chip BGA package to be compatible with the wider spacing geometries of typical mother board (or PCB) design rules. During the mounting process of the Flip Chip on a substrate, the chip is flipped upside-down, giving these chips the name “flip-chips.”
Solder balls or bumps are larger than normal wires or pins and improve electrical connection between the chip and the substrate. These balls also provide better thermal conduction from the printed circuit board or substrate to the chip. One downside to flip-chip BGA technology is the reduced access to the area between the solder balls and the complex air gap geometry. This gap is subject to environmental hazards arising from the different thermo-mechanical properties of the silicon chip and the organic substrate material. This can cause large thermally induced stresses on the flip chip solder balls in contact with the substrate. For this reason, a liquid encapsulant is inserted in the area between the flip chip and the substrate and then solidified. This process is called Flip-chip underfilling and is made by placing a liquefied encapsulant with a needle next to the underfill area at the edge of the chip to dispense the material at the base of the flip-chip. Capillary action, in association with liquid viscosity, seeps the dispensed encapsulant inwards to open spaces. Once the encapsulant is in place, thermal curing is performed to create a permanent bond. While different techniques are known to prevent the formation of voids in the gap area, the underfilling is a time-consuming process. A less viscous encapsulant may seep at higher rates but is likely to spread on the circuit board in other directions. As die sizes increase, so does the number of solder bumps used to connect the die to the substrate. In some instances, because of characteristics of the encapsulant, the dispensing machine must be used sequentially to place at different time intervals fractions of the needed encapsulant. In some cases 5 to 6 passes of dispense, seep, and dispense again must be taken to form clean void free underfill structures. In the environment where cycle time and dispensing machine is a crucial component of success, what is needed is a new type of package designed to optimize encapsulant underfill operations. Known devices include the placement of underfill encapsulation material around an entire perimeter of the semiconductor die where the material flows toward the center of the die where the time needed to completely fill the space between the die and the substrate is quite long due to successive passes of dispense. What is needed is new device able to reduce the time needed to fill this space by limiting the number of passes of dispense needed.
Flip Chip BGA substrates are generally made of successive layers of conductive material supported and insulated using insulating materials called dielectrics. One of the most common high-end substrates is BT buildup, made of a flame-resistant organic comprising a woven fiberglass mat impregnated with flame resistant BT resin. Substrates, while offering significant rigidity once the layers have been bonded together, are generally sold in 1600 micron or 800 micron standard thicknesses. The use of a rigid substrate is needed since these boards are often subject to a wide range of manufacturing steps designed to transform a basic substrate into a finished product to be used in the industry, called an integrated circuit package (FCBGA). Illustratively, during this process, substrates may be etched, laminated, drilled, cut, plated, soldered, silk screened, and subjected to chemical masking, coating, bridging, and the like. One advantage of thinner substrates is the ability to use smaller drill heads to perforate the substrate. The drilling of smaller holes means that less conductive material is needed to cover the interior of the hole and reduces undesirable impedance, saves manufacturing time, reduces waste, and is more cost effective. These advantages must be weighed against undesirable secondary effects such as warping of the surface of the substrate, difficulty of obtaining a stable surface, and weakening of the substrate during manufacturing operations. Thinner boards have lowered mechanical strength and impede the large scale industrialization of film-chip assemblies in a strip, matrix or array format.
Known devices include, among other things, an integrated circuit package substrate, a plurality of integrated circuit dies attached to the integrated circuit package substrate, and a stiffener strip attached to the integrated circuit package substrate and surrounding two or more of the plurality of integrated circuit dies. What is also needed is a new reinforced BGA substrate package with improved underfilling capacity and a BGA substrate package strip capable of reducing waste during the phases of extraction of the Flip Chip BGA substrates from the BGA substrate package strip. An improved substrate package and method are needed.